Research

Using isotopic analyses of primitive chondritic meteorites and their components, we can address questions about the dynamics and evolution of our early Solar System.

We are utilizing mass-independent isotopic anomalies in the stable isotopes of elements such as Cr and Ti as tracers for the incorporation of presolar materials into the solar nebula. In particular, the neutron-rich isotopes of Cr and Ti have a nucleosynthetic origin in supernovae and can be used to trace the incorporation of supernova materials into our Solar System, provide constraints on Solar System dynamics and mixing processes, and provide information on the genetic relationships between meteorites.

Torrano Z. A., Brennecka G. A., Williams C. D., Romaniello S. J., Rai V. K., Hines R. R., and Wadhwa M. (2019) Titanium isotope signatures of calcium-aluminum-rich inclusions from CV and CK chondrites: Implications for early Solar System reservoirs and mixing. Geochimica et Cosmochimica Acta 263: 13-30.

A key step in the planet-building processes involved in the formation of the rocky terrestrial planets like Earth and Mars was the accretion and differentiation of early-formed planetesimals and planetary embryos.

We are using the ²⁶Al-²⁶Mg (half-life ~0.72 million years) and ⁵³Mn-⁵³Cr (half-life ~3.7 million years) short-lived chronometers in combination with  the long-lived Pb-Pb chronometer (based on the decay of ²³⁸U and  ²³⁵U that have half-lives of ~4.5 billion years and ~700 million years, respectively) to determine precisely the timescales of accretion, melting, and differentiation of planetesimals that formed early in the history of the Solar System.

Srinivasan P., Dunlap D. R., Agee C. B., Wadhwa M., Coleff D., Ziegler K., Zeigler R., and McCubbin F. M. (2018) Silica-rich volcanism in the early solar system dated at 4.565 Ga. Nature Communications 9, 3036.

We are interested in deciphering the geologic history and evolution of Mars through geochemical and isotopic analyses of the martian meteorites. In particular, our prior work has focused on determining the redox conditions in the mantle and crust on Mars through studies of rare earth element abundances, as well as understanding the early differentiation history of Mars through investigations of the ¹⁴⁶Sm-¹⁴²Nd and ¹⁸²Hf-¹⁸²Hf short-lived isotope systems in Martian meteorites.

We also seek to understand the origin and history of water on Mars through studies of the volatile abundances and hydrogen isotope compositions of primary igneous materials in the martian meteorites.

We are additionally studying Icelandic basalts to understand the role of processes such as volatile degassing and fractional crystallization in the evolution of martian magmas.

Dunham E. T., Balta J. B., Wadhwa M., Sharp T. G., and McSween H. Y. Jr. (2019) Petrology and geochemistry of olivine-phyric shergottites LAR 12095 and LAR 12240: Implications for their petrogenetic history on Mars. Meteoritics & Planetary Science 1-25.

A little more than a decade ago, water was discovered in volcanic glasses returned from the Moon by the Apollo missions; this upended the long-held belief that the Moon was dry. Since then, lunar water has been analyzed in volcanic glass beads, rare melt inclusions, and primarily the Ca-phosphate mineral apatite. However, nominally anhydrous magmatic minerals like pyroxene, which may better represent the nature of primary lunar water, have largely been ignored because their water contents are so low and they are difficult to analyze.

Using our proven method for analyzing trace amounts of water in nominally anhydrous minerals, we are performing correlated micro-scale investigations of hydrogen isotope compositions, water contents, and the oxidation state of iron in pyroxenes from a variety of lunar basalts.

This work is anticipated to have significant implications for understanding the origin, distribution, and evolution of water in the Moon’s interior, and for furthering our understanding of the origin and evolution of the Moon.

Dr. Meenakshi Wadhwa was a co-investigator on NASA’s Genesis mission, and is a collaborator on the SAM instrument suite of NASA’s Mars Curiosity rover. At present, she is a member of the Hayabusa2 Initial Analysis Team for Chemistry and a member of the science team for the Mars 2020 mission. She is currently appointed as the Mars Sample Return Principal Scientist.